ML20203N950

Nuclear Safety Review Staff Investigation Rept I-86-110-SQN, Employee Concern 00-85-005-009, Sequoyah Located on Earthquake Fault, on 860124-30

ML20203N950
Person / Time
Site:	Sequoyah
Issue date:	03/03/1986
From:	Harwell E, Slagle F, Stevens W TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20203N908	List: ML20203N905 ML20203N911 ML20203N922 ML20203N940 ML20203N950 ML20203N964 ML20203N975 ML20203N986
References
I-86-110-SQN, NUDOCS 8605060236
Download: ML20203N950 (7)

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TENNESCEE VALLEY AUTHORITY NUCLEAR SAFETY REVIEW STAFF

. NSRS INVESTIGATION REPORT NO. I-86-110--SQN EMPLOYEE CONCERN: 00-85-005-009

SUBJECT:

SEQUOYAH LOCATED ON EARTHQUAKE FAULT DATES OF INVESTIGATION: JANUARY 24-30, 1986 INVESTIGATOR: N [d E./t. HARWELL DdTE /

REVIEWED BY: L A S S 3. M r-4_ _ *)/3/%

F. J. SLAGLE DATE APPROVED BY:

W. D. STEVENS 2/

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8605060236 860502 i PDR ADOCK 050003 7 l P  ;

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I. BACKGROUND A Nuclear Safety Review Staff (NSRS) investigation was conducted to determine the validity of an expressed employee concern as received by the Quality Technology Company (QTC)/ Employee Responso Team (ERT). The concern of record, as summarized on the Employee Concern Assignment Request Form from QTC and identified as 00-85-005-009, stated:

Sequoyah: Sequoyah Nuclear Plant is sited on an earthquake fault that runs from around Chattanooga to north of Knoxville. If there were an carthquake power plant structures could fail. CI has no further information. Construction Department concern.

II. SCOPE A. The scope of the investigation was determined from the st'ated concern of record to be two specific issues requiring investigation:

1. Is Sequoyah Nuclear Plant (SQN) located on an earthquako fault?

2. If there were an earthquake in the arca, would power plant structures f ail?

B. In conducting the investigation NSRS reviewed the SQN Final Safety-Analysis Report (FSAR), NRC Safety Evaluation Report (SER), and all supplements and correspondence between the NRC and TVA concerning the scismic design margins.

III.

SUMMARY

OF FINDINGS A. Requirements and Commitments

1. 10 CFR Part 100, Appendix A. " Seismic and Coologic Siting Criteria for Nuclear Power Plants"

2. Regulatory Cuide 1.60, " Design Responso Spectra for Soismic Design of Nuclear Power Plants"

3. Regulatory Cuide 1.61, " Damping Values for Seismic Design of Nuclear Power Plants"

4. Sequoyah Final Safety Analysis Report, Section 2.5, "Coology and Seismology"

5. NUREC-75/0.87, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," section 2.5.1,

" Basic Coologic and Seismic Information"; Section 2.5.2,

" Vibratory Ground Motion"; Section 2.5.'l, " Surface Faulting";

and Section 3.7.1, " Seismic Input" 1

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D. Findings

1. Section 2.5.1.5 of the FSAR states:

The controlling features of the geologic structure at the Sequoyah plant sito are the Kingston Thrust fault and a major overturned anticline which resulted from the movement along the fault. This fault lies about a mile northwest of the plant site and can be traced for 75 miles northeastward and 70 miles southwestward.

The fault dips to the southeast, under the plant site, and along it steeply dipping beds of the Knox dolomite have been thrust over gently dipping strata of the Chickamauga limestone. The distance from the plant site, about one mile, and the dip of the fault, 30 degrees or more, will carry the plane of the fault at 1 cast 2000 foot below the surf ace at the plant site.

The Missionary Ridge fault is a branch, or subsidiary, fault of the Kingston fault . . . it diverges from the Kinston fault; 3 miles southwest of the Sequoyah site. . . . .

2. Section 2.5.2.1 of the FSAR states, "There is no scologic evidence indicating that any of those faults could be considered to be " active" faults; that is, still undergoing movement."

3. The FSAR states that the nearest known epicenter from which an earthquake of damaging intensity (MMVII) may occur is 100 miles northeast of the SQU site. ("MM" is the Modified Mercalli Intensity Scalo.) A historical view of all carthquakes near the site area has not revealed any of intensity greater than MMV-VI, which is below the damaging intensity (MMVII). Although an earthquake of the KKVIII intensity has not occurred within 250 miles of the plant site, this intensity is assumed to occur at the site for the purpose of evaluating the Safe Shutdewn Earthquake (SSE). The maximum acceleration for an carthquake of this intensity is estimated to be 0.14g.

4. The FSAR states that the plant is designed so that all structures, systems, and components important to safety will remain functional when subjected to an SSE having maximum horizontal acceleration of 0.188 and maximum vertical ground acceleration of 0.12g. However, as a result of the development of the site specific responso spectrum in 1979, an SSE of 0.22g was considered.

5. In the SQN SER (Ref. 2), the NRC concluded that there woro no known geologic structures that would cause surface displacement or would tend to localize earthquakes in the site vicinity. The SER stated:

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In terms of actual spectral response for this period, the present design is at 0.18g while the 84th percentile (hereafter called the site-specific safe shutdown carthquake) would be at 0.28g. At periods greater than 0.35 seconds, the present design always exceeds the site-specific safe shutdown earthquake.

The NRC concluded that the difference in seinmic hazard between the present design at SQN and the site-specific response spectrum is not substantiated. The report alco stated:

In addition, because of such factors in the plant design as usage of lower-bound material properties, conservative analysis methods, and loading combinations that include low-occurrence-probability secondary events, a substantial additional margin to resist seismic loading exists in the plant's structures and equipment.

Based on all the above, we conclude that the present design basis for the Sequoyah Nuclear Plant is adequate to withstand the effects of earthquakes without loss of capability to perform the required safety functions.

However, because the design spectra did fall below the site-specific spectra, the NRC requested verification and qualification of the additional margins of selected critical sections of the reactor building and auxiliary building.

6. In reference 3, the NRC stated that they had ascertained that the limiting design of the steel containment was not seismic loads, but loss-of-coolant pressure loads. As a result of their review, the NRC concluded that the seismic Category I structures are acceptabic for seismic loadings calculated on the basis of the 84th percontile site-specific response spectra when used in conjunction with the damping values recommended by Regulatory Guide 1.61.

7. In December 1979, the ACRS recommended that TVA continue and expand the study of the seismic design margins for the SSE. In May 1980. TVA described by letter (Ref. 5) the details of the expanded coismic design margin investigation. In reference 4, the NRC concluded that completion of the expanded design margin program within the next 18 months was acceptable and that operation at full power need not be delayed pending completion of the reanalysis.

8. TVA presented the results of the expanded design margin study to the NRC on March 29 and 30, 1982, in Knoxyllie and the NRC reviewer did not disageco with TVA conclusions.

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IV. CONCLUSIONS AND RECOMMENDATIONS A. Conclusion The concern of record as stated was not substantiated because:

1. The SQN is not located directly on the earthquake fault.

2. The seismic analysis performed by TVA and accepted by the NRC concluded that adequate design margins exist for all critical components and structures to withstand the anticipated earthquake loads without losing their capability to perfoon their required safety functions.

B. Recommendations None 0

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l DOCUMENTS REVIEWED IN INVESTIGATION 1-86-110-SQN i AND REFERENCES

1. Sequoyah Final Safety Analysis Report R2, Section 2.5, "Goology and Seismology" l

2. Sequoyah Safety Evaluation Report, NUREC-0011 March 1979, Docket Nos. l 50-327 and 50-328

3. Sequoyah SER, NUREG 0011, Supplement 1 dated February 1980

4. Sequoyah SER, NUREG 0011, Supplement 2, dated August 1980

5. TVA letter from L. M. Mills to A. Schwencer of URC dated May 5, 1981 (A27 810505 028)

6. TVA letter from L. M. Mills to E. Adensam of NRC dated March 1, 1982 (A27 820301 002)

7. 10 CFR Part 100. Appendix A. " Seismic and Coologic Siting Criteria for Nucicar Power Plants"

8. Regulatory Guide 1.60 R1, " Design Responso Spectra for Soismic Design of Nuclear Power Plants"

9. Regulatory Guide 1.61, " Damping Values for Soismic Dosign of Nucicar Power Plants"

10. NUREG-75/087, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants" 0141T 5

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. TO A H god 94H (OPWWM) .

73 , C- m. -*~V iNITED STATES GOVERNMENT Mentorandum Texxesses vattsv Aurzioniry

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TO: H. L. Abercrombie, Site Director, Sequoyah Nuclear Plant 7,, . c'-I'd 5^' # %;

FR0h: K. W. Whitt, Director of Nuclear Safety Review Staf f E3A8 C- K -

. .q ,3 0 0 DATE: MAR 0 61986 -

SUBJECT:

NUCLEAR SAFETY REVIEW STAFF INVESTIGATION REPORT TRANSMITTAL y'p-j, f f r _,- . _

Transmitted herein is NSRS Report No. I-86-129-SON 2fr P ._ _

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Subject SECOND FOLLOW-UP OF OEB RECORDS INVESTICATION 1-8 3 =434G-- 1 Concern No. SOP-6-002-001 l ,

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The attached report contains one Priority 3 [P3] recor=endation which in this case requires you to continue corrective action as indicated in the

, report. No formal response is required for this report unless you disagree with the proposed action. Please notify us if actions taken have been completed sooner. Should you have any questions, please contact W. D. Stevens at telephone 6231-K .

Recom.end Reportability Determination: Yes No I

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Director, NSRS/ Designee ~

f WDS:GDM f Attachment cc(Attachmentk W. C. Bibb, BFI W. T. Cottle. kmu m James P. Darling, BLN R. P. Denice, LP6N40A-C G. B. Kirk, SQN D. R. Nichols, E10A14 C-K QTC/ERT, Watts Bar Nuclear Plant i Eric Slifer, LP6N48A-C J. H. Sullivan, SQN Q5S7U p,

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